Both MozCast and SearchMetrics are preparing and updating their search tracking tools to document the changes in the mobile search results by April 21st.

Marcus Tober announced it on their blog and on Twitter saying "NEW: Mobile SEO Visibility." Indeed, you can now track your ups and downs based on search query data specifically in the mobile friendly Google search results on Search Metrics. It is live and in beta and here is a chart:

This is going to be key to see which sites prepared and which did not and how much it hurt them for not preparing and how much it helped them by preparing.

Pete Meyers, the man behind MozCast announced on Twitter that he is working on tracking overall SERP changes for the Google mobile results by April 21st. He said:

MozCast Mobile is in the works. Goal is to have data by end of March and measure the 4/21 update. Let's not take Google's word for it.

So if Google won't give us the percentages changed, these tools should come close.